1. Field of the Invention
This invention relates to a variable steam flow assembly for a steam iron and more specifically to a variable steam flow assembly which allows an operator to select from a finite number of steam flow rates which can be more accurately controlled than valves used in conventional steam irons and is less susceptible to mineral deposits.
2. Description of the Prior Art
Steam irons having variable steam flow rates are known in the art. Examples of such steam irons are disclosed in the following U.S. Pat. Nos.: 2,887,799; 3,130,507; 3,136,080; 3,165,843 and 3,263,350. In general, these irons have a water reservoir which communicates with a steam generator by way of a metering valve. Such metering valves consist of an orifice or valve seat which cooperates with a valve rod, generally tapered or stepped at one end, to control the flow of water from the water reservoir to the steam generator. The valve rod is generally connected to a mechanical linkage which, in turn, is connected to an actuator located on the outside of the iron housing to allow the operator to control the axial movement of the metering rod with respect to the valve seat to obtain the desired steam flow rate. With such valves, the position of the valve rod with respect to the valve seat controls the steam flow rate. The valve rod may also be fully inserted into the valve seat to close off the water supply to the steam generator such that the iron can be used as a dry iron.
However, with such valves, it is relatively difficult to accurately control the axial position of the valve rod with respect to the valve seat, thus making it difficult to accurately control the steam flow rate. Such valves are also subject to inaccuracies in the steam flow rate due to manufacturing tolerances in the valve rods and the valve seats. Moreover, it is difficult to control the flow rate with such metering valves because of the exposure of the valve rod and valve seat to the steam generator making it susceptible to mineral deposits due to spattering resulting from the boiling of water droplets in the steam generator.
Some prior art steam irons have attempted to provide means for self-cleaning, of an iron. For example, U.S. Pat. No. 3,889,406 discloses a metering valve which includes a valve seat and a tapered valve rod mounted to allow the tapered end of the valve rod to be completely spaced apart from the valve seat to allow relatively large quantities of water to flow through the valve and into the steam generator to flush out carbonized lint and loose residues in the soleplate. However, such a self-cleaning feature is unlikely to clean all mineral residues from the metering valve itself.
In U.S. Pat. No. 4,197,664, a metering valve having a valve seat and a metering rod tapered at one end is allowed to extend all the way through the valve seat to allow residues formed in the valve seat to be scraped off. However, as heretofore stated, it is difficult to control the flow rate of such a valve because of the difficulty in controlling the axial position of the valve rod with respect to the valve seat.